Orthodontics is a dental specialty that treats malocclusion through the movement of teeth as well as the control and modification of facial growth. This process is usually accomplished by using a continuous mechanical force to induce bone remodeling, thereby enabling the teeth to move to a better position. In this approach, orthodontic appliances provide a continuous static force to the teeth via an archwire connected to brackets affixed to each tooth or via a removable appliance such as an aligner, or some similar accessory that fits over the dentition. As the teeth slowly move due to the applied force, the force dissipates, and the archwires must be adjusted to add additional force and to continue the desired tooth movement. Although effective, this widely accepted approach takes about twenty-four months on average to achieve success.
Researchers have long postulated that a pulsating force might also be used to move teeth more rapidly and to ease the discomfort of traditional orthodontics. Mao was probably the first to prove that the use of cyclic forces could improve orthodontic straightening in rabbits (see U.S. Pat. No. 6,684,639, U.S. Pat. No. 6,832,912, U.S. Pat. No. 7,029,276). Certain dynamic loading patterns (cycling force with rest periods) were shown to greatly increase bone formation compared to static dynamic loading. Inserting rest periods is now known to be especially efficacious as it allows mechanosensitivity to be restored to the bone tissue. A point of diminishing returns is reached within each loading session. Therefore, intermittently loading force can increase the rate of bone formation significantly.
US2008227046, by OrthoAccel Technologies Inc., describes the first device specifically designed to capitalize on the Mao research and has been very successfully marketed as “AcceleDent™.” This device has been shown in clinical trials to reduce patient treatment time by as much as 50% and may be the biggest advance in orthodontics since the aligner was first invented. Further, an updated model with a smoother and quieter motor (as described in US2010055634) has achieved very high patient compliance and satisfaction rates.
Although AcceleDent™ is a very successful product, there is always room for continued improvement in this field. In particular, it would be advantageous if vibration could be combined with another modality, so that remodeling is stimulated by two mechanisms of action, and infrared light may offer some possibilities in this regard.
Infrared (IR) light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometers (μm), and extending conventionally to 300 μm. Infrared light is used in industrial, scientific, and medical applications, and its power in medical applications has yet to be fully realized.
A laser is a device that emits light (electromagnetic radiation) through a process of optical amplification based on the stimulated emission of photons. The term “laser” originated as an acronym for Light Amplification by Stimulated Emission of Radiation. The emitted laser light is notable for its high degree of spatial and temporal coherence, unattainable using other technologies. Additionally, a laser usually produces light of a single wavelength, e.g., it is monochromatic.
Most so-called “single wavelength” lasers actually produce radiation in several modes having slightly different frequencies (wavelengths), often not in a single polarization. Therefore, the terms “monochromatic” or “single wavelength,” actually includes a small range of frequencies (+/−a few percent). Further, although temporal coherence implies monochromaticity, there are even lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously. There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit. However all such devices are classified as “lasers” based on their method of producing that light: stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies.
Light Emitting diodes are another source of light that is mostly monochromatic. Strictly speaking, an LED is not a laser, although popular culture usually does not make this distinction. Lasers are closer to monochromatic, collimated (non-divergent) and coherent (wavelengths in-phase). In contrast, ordinary LED's are neither coherent nor collimated and generate a somewhat broader band of wavelengths. Another difference between the two is the power output. The peak power output of lasers is measured in watts, while that of LED's, is measured in milliwatts. Also, LED's usually have a 50% duty cycle, meaning that they are “on” 50% of the time and “off” 50% of the time regardless of what frequency (pulses per second) setting is used.
It is possible, however, to produce an LED, wherein the use of multiple semiconductor layers allows for the production of light of the same frequency and phase. Such LEDs are often called “laser diodes,” indicating a higher degree of coherence and narrower frequency range.
Lasers have long been used in dentistry. For example, a dental laser is a type of laser designed specifically for use in oral surgery or dentistry. Soft tissue lasers are used to safely treat and destroy bacteria in gum pockets, preventing infection thereby allowing the gum tissue to return to a healthy state. The two soft tissue lasers commonly in use are the NdYag Laser and diode lasers.
Hard tissue lasers are also available, and are used to remove old composite fillings, repair cavities, and prepare teeth for bonding. As with soft tissue lasers, they dramatically minimize discomfort and allow the dentist to treat teeth with more precision. One laser in use is the erbium laser, which works on the hard tissues, including tooth and bone. It is of particular benefit, as providing less pain than older technology.
Other lasers have been used for imaging purposes. The Diagnodent® laser, for example, is a low level laser light which is placed against the tooth and can detect very early decay. In this small hand held device, where the laser light comes in contact with the tooth, two-way hand piece optics allows the unit to simultaneously quantify the reflected laser light energy. A clean healthy tooth structure shows little or no fluorescence, resulting in very low number readings on the display. However, carious or decayed tooth structure will emit fluorescence light, resulting in elevated number readings on the display. An audible sound is produced as well, which varies according to the amount of decay.
Lasers have also been employed in dentistry for curing purposes. Argon laser curing of traditional light-activated composite resins, for example, has been shown to be superior over conventional light-curing with respect to bond failure and chairside time, although the incidence of decalcification seems to be similar.
Finally, lasers have also been used for tooth whitening. Different types of energy can be used in this procedure, with the most common being halogen, LED, or plasma arc. Halogen light is the best source for producing optimal treatment results, and the ideal source of energy should be high energy to excite the peroxide molecules without overheating the pulp of the tooth. Lights are typically within the blue light spectrum as this has been found to contain the most effective wavelengths for initiating the hydrogen peroxide reaction.
There have also been consumer devices designed for teeth whitening. U.S. Pat. No. 7,645,137, for example, describes a hand moldable dental tray that has a light source, and can be used with a whitening gel. The device appears to only contact teeth of the upper jaws and would need to be turned over for the lower teeth, whereon the gel would have a tendency to fall out. Further, no details about the light source are provided and its connection to the tray, so it is unclear how or if the device works. U.S. Pat. No. 7,331,784 describes a light tray, which again appears to contact only the upper teeth, and an exterior blue LED connected to the tray via cable or cord and blinks during use. Since these devices are designed for teeth whitening, it may suffice to treat only the upper teeth since those are the most visible. However, neither device is suitable for orthodontic uses.
US20120214122 describes a clear mouthpiece that does contact both upper and lower teeth, together with a removable exterior portion or lightbox that has a number of blue LEDs that shine light through the clear mouthpiece and contains all of the needed circuitry. However, there is noting to guide the light and much of it will be dissipated without effect, reducing the overall efficacy of the device per unit of power consumed.
To our knowledge a laser based orthodontic remodeling device has never been proposed or achieved, nor has a portable IR laser bite plate been designed specifically for orthodontic remodeling.